Scientists Create Schrödinger-Cat State With Record-Long Lifetime

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Quantum Breakthrough: Scientists Create Schrödinger-Cat State With Record-Long Lifetime

March 17, 2025

USTC researchers created a long-lived Schrödinger-cat state, boosting quantum metrology and precision measurements. Their findings open new possibilities for quantum computing and fundamental physics.

A research team led by Prof. Zhengtian Lu and Researcher Tian Xia from the University of Science and Technology of China (USTC) has successfully created a quantum state with a lifetime on the scale of minutes using optically trapped cold atoms. This breakthrough significantly improves the sensitivity of quantum metrology measurements. Their findings were published in Nature Photonics.

In quantum metrology, particle spin serves as a powerful tool for measuring magnetic fields, inertia, and various physical phenomena. It also has the potential to uncover new physics beyond the Standard Model. A high-spin Schrödinger-cat state, a superposition of two maximally opposed spin states, offers unique advantages for precision spin measurements.

The high spin quantum number enhances the precession frequency signal, improving measurement resolution. Additionally, cat states exhibit resistance to certain environmental disturbances, reducing measurement noise. However, a key challenge in experimental applications is maintaining long coherence times, which are crucial for the practical use of cat states in precision measurements.


Overcoming the Challenge of Coherence Time:

To address this challenge, the research team first trapped 173Yb atoms with a spin of 5/2 in an optical lattice. By controlling laser pulses to induce nonlinear light shifts on the ground states of the atoms, they successfully prepare a superposition state consisting of two spin projections, +5/2 and -5/2. This state, namely the Schrödinger-cat state, exhibits enhanced magnetic field sensitivity and experiences identical light shifts in the optical lattice, residing within a decoherence-free subspace. Therefore, it is immune to intensity noise and spatial variations of the lattice.

Experimental results indicated that the coherence time of this cat state exceeded 20 minutes. Utilizing Ramsey interferometry, the researchers confirmed that the phase measurement sensitivity approached the Heisenberg limit.

This long-lived Schrödinger-cat state paves a new way for atomic magnetometry, quantum computations, and the exploration of new physics beyond the Standard Model.

Reference: “Minute-scale Schrödinger-cat state of spin-5/2 atoms” by Y. A. Yang, W.-T. Luo, J.-L. Zhang, S.-Z. Wang, Chang-Ling Zou, T. Xia and Z.-T. Lu, 32 October 2024, Nature Photonics.
DOI: 10.1038/s41566-024-01555-3

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USTC researchers achieved a long-lived Schrödinger-cat state, improving quantum measurement precision and enabling new advances in physics and technology. Credit: SciTechDaily.com

The spins of 173Yb atoms form a Schrödinger-cat state within a one-dimensional optical lattice. Credit: Yang et al.